Channel Feedback Reporting for Shared Frequency Spectrum

1. A method of wireless communication at a user equipment (UE), comprising: communicating with an evolved node B (eNB) over a frequency channel of a shared frequency band; receiving a data transmission from the eNB over the frequency channel of the shared frequency band; determining acknowledgement/negative acknowledgement (ACK/NACK) information for the data transmission; and transmitting the ACK/NACK information in a clear channel assessment (CCA) exempt feedback transmission to the eNB via the frequency channel of the shared frequency band, wherein the ACK/NACK information is mapped to designated resources of an uplink control channel structure for the CCA-exempt feedback transmission.

2. The method of claim 1 , further comprising: determining uplink scheduling feedback or channel state information (CSI) feedback; and transmitting, in the CCA-exempt feedback transmission, the uplink scheduling feedback or the CSI feedback.

3. The method of claim 2 , further comprising: determining a target modulation and coding scheme (MCS) for a subsequent data transmission based at least in part on channel measurements of one or more reference signals associated with the data transmission; and wherein the transmitted CSI feedback comprises an indicator associated with the target MCS.

4. The method of claim 3 , further comprising: identifying a current MCS for the data transmission; and determining a channel quality delta between the current MCS and the target MCS, wherein the indicator associated with the target MCS comprises the channel quality delta.

5. The method of claim 3 , wherein the one or more reference signals comprise any of a cell-specific reference signal (CRS), a demodulation reference signal (DM-RS), a UE-specific reference signal (UE-RS), or combinations thereof.

6. The method of claim 5 , wherein the determining the target MCS for the subsequent data transmission comprises estimating a quality of a channel from the eNB based at least in part on the CRS and an identified precoding matrix for the data transmission.

7. The method of claim 1 , wherein the uplink control channel structure comprises a subset of frequency resources of the frequency channel of the shared frequency band.

8. The method of claim 1 , wherein the start of the CCA-exempt feedback transmission occurs less than a predetermined CCA time period from an end of the data transmission.

9. The method of claim 1 , wherein the frequency channel of the shared frequency band comprises an enhanced component carrier (eCC) configured for the UE in a standalone operation mode.

10. The method of claim 1 , further comprising: receiving a feedback configuration for providing feedback for transmissions over the frequency channel of the shared frequency band, wherein the feedback configuration indicates providing the feedback in the CCA-exempt feedback transmission, a CCA-compliant feedback transmission, or combinations thereof.

11. An apparatus for wireless communication, comprising: a processor; memory in electronic communication with the processor; and instructions stored in the memory and operable, when executed by the processor, to cause the apparatus to: communicate with an evolved node B (eNB) over a frequency channel of a shared frequency band; receive a data transmission from the eNB over the frequency channel of the shared frequency band; determine acknowledgement/negative acknowledgement (ACK/NACK) information for the data transmission; and transmit the ACK/NACK information in a clear channel assessment (CCA) exempt feedback transmission to the eNB via the frequency channel of the shared frequency band, wherein the ACK/NACK information is mapped to designated resources of an uplink control channel structure for the CCA-exempt feedback transmission.

12. The apparatus of claim 11 , wherein the instructions are operable to cause to: determine uplink scheduling feedback or channel state information (CSI) feedback; and transmit, in the clear channel assessment (CCA)-exempt feedback transmission, the uplink scheduling feedback or the CSI feedback.

13. The apparatus of claim 12 , wherein the instructions are operable to cause to: determine a target modulation and coding scheme (MCS) for a subsequent data transmission based at least in part on channel measurements of one or more reference signals associated with the data transmission; and wherein the transmitted CSI feedback comprises an indicator associated with the target MCS.

14. The apparatus of claim 13 , wherein the instructions are operable to cause to: identify a current MCS for the data transmission; and determine a channel quality delta between the current MCS and the target MCS, wherein the indicator associated with the target MCS comprises the channel quality delta.

15. The apparatus of claim 13 , wherein the one or more reference signals comprise any of a cell-specific reference signal (CRS), a demodulation reference signal (DM-RS), a UE-specific reference signal (UE-RS), or combinations thereof.

16. The apparatus of claim 15 , wherein the determining the target MCS for the subsequent data transmission comprises estimating a quality of a channel from the eNB based at least in part on the CRS and an identified precoding matrix for the data transmission.

17. The apparatus of claim 11 , wherein the instructions are operable to cause to: receive a feedback configuration for providing feedback for transmissions over the frequency channel of the shared frequency band, wherein the feedback configuration indicates providing the feedback in the CCA-exempt feedback transmission, a CCA-compliant feedback transmission, or combinations thereof.